1. Field
Aspects of the present invention generally relate to a toner supply control processing of supplying toner into a containing unit.
2. Description of the Related Art
Electrophotographic image forming apparatuses consume toner contained in a containing unit to form a toner image based on image data input to the image forming apparatus.
It has been known that in the image forming apparatus, a density of a developed image (toner image) changes in accordance with a ratio [wt %] (hereinafter, referred to as toner density) of toner in a developer contained in a containing unit. Thus, the image forming apparatus needs to supply toner into the containing unit from a container, so that the toner density of the toner contained in the containing unit remains a target density (target ratio [wt %]).
A conventionally known image forming apparatus determines a toner supply amount based on an amount (consumption amount) of toner in the containing unit, and a difference between the toner density of the toner and a target density. An image forming apparatus discussed in US2013/0202319 determines the toner supply amount based on the estimated consumption amount of the toner based on image data, the difference between the toner density of the toner contained in the containing unit and the target density, and a cumulative value of the difference.
The estimated consumption amount of the toner obtained by a calculation is only theoretical, and thus is slightly different from the actual consumption amount of the toner in the containing unit. Moreover, the amount of toner, supplied to the containing unit from the container, is inaccurate. Thus, the toner density of the toner in the containing unit might not reach the target density even when the toner is supplied to the containing unit, based on the toner supply amount determined as described above. Thus, in US2013/0202319, a correction amount, by which the toner density of the toner is corrected, is determined to achieve the target density based on a difference between the toner density of the toner and the target density. Then, the toner supply amount is determined by adding the correction amount to the consumption amount.
However, the image forming apparatus discussed in US2013/0202319 has a problem when an amount of toner in the containing unit is larger than a target amount. The problem occurs when a plurality of toner images requiring a large toner consumption is formed after a plurality of toner images requiring only a small toner consumption is formed. Specifically, the toner is not swiftly supplied to the containing unit after the toner image requiring a large toner consumption has started to be formed.
A correction amount, calculated while the toner images requiring only a small toner consumption are formed in the state where the amount of toner in the containing unit is larger than the target amount, is value that reduces the supply amount of the toner. Specifically, the cumulative value of the difference between the toner density and the target density, involved in the calculation of the correction amount, is value by which the supply amount of toner is reduced.
Thus, when the toner image requiring a large toner consumption is formed after a plurality of toner images requiring only a small toner consumption is formed, the correction amount by which the supply of toner is reduced might exceed the toner consumption amount estimated with respect to the toner image requiring a large toner consumption. As a result, the toner is not supplied to the containing unit, even though the toner in the containing unit is decreasing because the toner image requiring a large toner consumption, has started to form.